Because of an odd mix of conditions, outlooks for the crop have been all over the map. The winter and spring were unusually mild, giving some hope that the walnut trees would produce heavily. But then the drought hit.

Proponents cite growing evidence that brain damage can occur with a series of soft impacts to the head, rather than a hard blow. But others say heading is a vital part of the game that needs to be taught.

Some worry the government's assertion could open up people who practice bondage, dominance, sadism and masochism — or BDSM — to criminal charges for consensual acts they're already performing, said Susan Wright, founder of the Baltimore-based National Coalition for Sexual Freedom.